HK1256471B - Gas blanketing system for low-pressure hydocarbon tanks - Google Patents

Description

Gas blanketing system for low pressure hydrocarbon canister

Technical Field

The present invention relates to maintenance of gas blanketed hydrocarbon canister systems. More particularly, the present invention relates to a system and method for blanketing a gas over a hydrocarbon fuel in a small underground storage tank to resist corrosion within the tank.

Background

Small and medium size (generally considered to be below about 50000 gallons) underground storage tanks made of steel or fiberglass are commonly used to store and distribute petroleum hydrocarbon products from a wide variety of facilities. Some of the most common hydrocarbon products are diesel and gasoline. These tanks are typically located at retail gasoline stations.

There is an existing and growing need to protect such infrastructure from degradation due to corrosion. Although there is more than one problem of corrosion associated with fuel tanks, it is clear that a wide range of microorganisms of the genus Acetobacter grow in the air space (empty space) of underground storage tanks and that one by-product of this growth is acetic acid. There are several problems that this acid causes directly and indirectly: the fine particles interfere with fuel delivery by clogging filters and wearing delicate meter blades and gears, thereby destroying the structural integrity of tanks, quick-open valves, and other service station equipment. One solution, keeping the air gap dry and reducing or eliminating oxygen in the empty part of the tank, would be to significantly reduce or prevent acidification. Currently, there are no commercially available, permanently installed, environmental control systems that use nitrogen or other inerts to control the air gap environment within small or medium-sized tanks in retail stores, buildings, and small commercial sites.

There are inert gas blanketing systems designed for refineries, mass storage and transfer terminals. These large, above and below ground, high and low pressure fuel storage tanks for gasoline and diesel use inert gas blanketing systems.

For low pressure small or medium sized tanks commonly used for and intended for storing and dispensing gasoline or ultra low sulfur diesel fuel, there is no air gap (free space environment) environmental control system using nitrogen or inert gas blanketing design principles.

There are inert gas blanketing systems designed for refineries, mass storage, airport terminals and transfer terminals. The API2000 protocol is found in refineries, pipeline terminals and airports worldwide and is used to prevent corrosion of internal tanks and as a safety guarantee to reduce the exposure potential of contained hydrocarbons.

It is therefore an object of the present invention to provide a gas blanketing system for small and medium size tanks.

It is another object of the present invention to provide a controlled, self-contained overlay system for producing and distributing hydrocarbons.

It is yet another object of the present invention to provide a system to generate and distribute the cover gas while providing the cover gas in the gas space of the hydrocarbon canister.

It is yet another object of the present invention to provide a system to provide a cover gas and a volatile corrosion inhibitor into the air space and/or void of a hydrocarbon canister.

It is therefore an object of the present invention to provide a method for covering various surfaces in a fuel storage and delivery system.

It is another object of the present invention to provide a system for properly distributing VCIs in a fuel system.

It is yet another object of the present invention to measure and maintain the system integrity of a pressure controlled overlay system.

It is yet another object of the present invention to control and/or prevent the undesirable release of hydrocarbon vapors from the canister.

It is yet another object of the present invention to inhibit and/or prevent corrosion of the tank wall.

Disclosure of Invention

The starting point of the invention and the proposed use in retail locations is unconventional corrosion (hereinafter aggressive corrosion), which has been documented in various cases over the last few years. As the use of alcohol added to gasoline products is becoming more common, it has been recognized that the penetration of water or mixing with alcohol gasoline blend fuels (also known as electronic gases, representing various blends of ethanol and gasoline that are currently on sale or potentially available in the near future) is reduced because alcohol will absorb water as it enters the fuel dispensing system. Various problems may arise when water enters the fuel system. One such problem occurs when the alcohol content reaches the water saturation level of the fuel at a particular temperature. If the temperature of the fuel is reduced (he can for environmental reasons) the alcohol/water mixture will separate and drop to the bottom of the tank. This process is called phase separation. Fuel should not be sold at this point because alcohol is one component that supports the octane rating of the fuel and if phase separation occurs, the octane rating is reduced. This new liquid phase separated fuel is generally more corrosive than the normal alcohol/gasoline fuel blend. This new liquid also has alcohol and water to provide the nutrients needed to support the rapid growth of microorganisms. One by-product of microbial growth is acetic acid, a corrosive fluid that is harmful to fuel delivery equipment, vehicle fuel supply equipment, and motor components.

Similarly, diesel fuel is now also blended with biodiesel. The water in this biodiesel also supports rapid microbial growth, acetic acid by-product of the microbes, and the resulting aggressive corrosion.

Nowadays, the reduction of sulphur in fuels is also a further cause of tank air voids and acidification of fuels, since higher concentrations of sulphur can inhibit bacterial growth in fuels.

One activity of getting water into the tank where the fuel is stored is the act of dispensing the fuel from the tank. As the fuel leaves the canister, a low pressure (lower pressure) region builds up in the canister as the fuel leaves and ambient air flows into the canister from the outside. This air vapor has moisture that condenses on the inner surface of the canister. The condensed water vapor provides a wet surface on the exposed portion of the can, referred to as the air gap or headspace of the can. Water and oxygen provide an ideal environment for bacterial growth.

As more fuel leaves the canister, more air is drawn into the canister. More air carries more water vapor and therefore more condensate deposits on the exposed portions of the cans. At some point, water begins to drip from the top of the tank and flow into the fuel along the sides of the tank, thereby causing and assisting bacterial growth in the fuel.

Another activity that leads to condensation inside the tank is exposure or at least partial exposure to large temperature changes, such as above ground storage tanks or tanks that are only partially buried and above ground storage tanks encased in concrete. In these cases, the tank is heated during warmer periods of the day and by exposure to sunlight, and the tank is also exposed to cooler environments during storms, rain, snow and nights. These activities create large temperature differences, and thus pressure differences expel vapor and absorb moisture.

Another activity of water entering the tank system is when rain seeps through the ground or surface water covers the top of the tank. Water may enter the tank through holes, plugs and fittings in the tank that allow equipment to be installed, or provide access, or fuel access, etc.

It is beneficial to continuously monitor the thickness of the can to check whether there is a potential leak at the described entry point in the can top.

As previously mentioned, one by-product of moisture, oxygen, bacteria and hydrocarbons is acetic acid, and the headspace of the tank is acidified. This acidified vapor is pressurized during fuel delivery to the canister (the entire headspace of the canister is pressurized). This pressure is intended to be returned by purposely prepared venting methods and can be made to exit through any available opening, including threads, gasketed manholes, and no opening that effectively seals against the pressure differential between the tank and the tank.

The motivation for the initial testing requirement for inert gas nitrogen blanketing was to demonstrate or refute positive effect environmental control to prevent the acidic atmosphere and its corrosive effects on the design integrity of ULSD fuel storage tanks, their connection fittings and components.

One benefit mentioned when filling the headspace of a fuel storage tank with an inert gas is the reduction of the chance of a flash fire, such as those commonly found in these tanks due to a lightning strike to the vent or other metallic connection to the headspace of the tank, or electrostatic discharge from the fuel supply or filling process in communication with the headspace of the tank, which are known and recognized problems in the art.

Initial testing motivation for inert gas nitrogen blanketing was to demonstrate or refute environmental control to prevent acidic air gap atmospheres and their impact on the design integrity of fuel storage tanks, their connection fittings and components.

As more and more ORVR equipped vehicles are refueled in conventional vapor recovery capture areas, the phase II vapor harvesting system is adversely affected because the ORVR devices do not return vapor from the vehicle as previous generation phase II devices were designed. As the number of modules in an ORVR equipped vehicle increases, the vapor recovery function to prevent hydrocarbon emissions has been compromised and vapor recovery failure alarms have increased. This has frustrated the owner of the gasoline station because of the downtime to handle the alarms and the substantial increase in testing costs forced by these alarms.

Efforts to control excessive and variable hydrocarbon emissions by existing vapor recovery systems become increasingly inefficient, depending on which ORVR equipped vehicle fueling model is used during licensing, system design, and service station construction. Some gasoline station operators are aware of fuel losses and excessive emissions, especially because the pressure fluctuations in the ullage of the tank are far from the design parameters of existing vapor control devices.

Another advantage of introducing nitrogen only in the air gap is that nitrogen is lighter than most hydrocarbons, and is always the first to be expelled during any fuel refilling of the canister. This reduces evaporative fuel losses for the owner of the canister. The greater the amount of product sold or transferred per day, the greater the economic value of this loss reduction.

Nitrogen transfer during fuel refilling of the tank is also beneficial for public transportation because the returned tanker is no longer filled only with explosive vapors, but with reduced fuel vapors and reduced oxygen content, thereby providing safer transportation for the driver and the public.

Another benefit of introducing compressed inert gas into the air gap is that the amount of fuel vaporized is reduced. Any pressure applied to the fuel will reduce the amount of evaporation that occurs and will significantly reduce the evaporation of fuel that is currently held in low pressure systems, especially those tank systems that have a vacuum on the tank system.

Another benefit of introducing an inert gas into the air gap is that the oxygen content in the air gap is reduced. Oxygen is one of the components required for the proliferation of many bacteria that produce acid.

One benefit of blanketing the roof with nitrogen is that nitrogen molecules are larger than some hydrocarbon molecules and other air molecules, and also lighter than some hydrocarbon molecules and other air molecules, so that nitrogen cannot pass through some of the smallest openings of the roof. If nitrogen is not present, hydrocarbons will pass through the same openings, resulting in surface or air contamination.

Another aspect of the invention is to provide a dry inert gas to the interstitial space of a double-walled can. The interstitial regions are where moisture accumulates. The flowing dry inert gas is able to remove the moisture present and prevent the accumulation of new moisture. This ability can reduce or eliminate the oxygen content in the interstitial space of a double-walled can, thereby preventing or inhibiting bacterial growth. This can be achieved by periodic flushing or by drawing or pushing other air molecules via a constant flow.

The effect of the successful application of these criteria is to collect a sufficient amount of reliable and relevant data to see if blanketing the empty space of the storage tank with inert gas nitrogen would inhibit or prevent the formation of acidic acids in some tanks that hold, store and dispense fuel. We actually have data from both tanks to confirm this for N2 and multiple studies specifically combining water, water vapor, fuel and oxygen to produce acid.

The reduction of rust particles in the tank fuel means that the rust will no longer be pumped by the submersible pump, resulting in wear on the pump assembly and pushing of the rust into the dispensing meter. This therefore reduces wear on the meter and reduces the need to frequently replace blocked filters. Currently, as fuel is delivered, rust moves with the fuel, and rust particles typically accumulate together due to the repeated flow pattern of the fuel droplets. The rust particles provide an important area for the bacteria to root and become sticky, so that these bacteria are better able to protect themselves from the antimicrobial agent.

Typically, retail tanks store conventional and custom blends of diesel and biodiesel, gasoline and ethanol, and other commercial liquid hydrocarbon fuels. In addition, these tanks typically have a capacity of 50000 gallons or less, are low pressure, and may be installed above ground or underground. The benefits of inertly filling a fuel tank with nitrogen are well known in the art.

As such, the present invention includes:

1. an air compressor generates the pressurized air required by the nitrogen generator.

2. The compressed air storage tank reduces the need to run the air compressor continuously, thereby saving electrical energy, etc. The compressed air from the compressed air storage tank is cooled and filtered before use with the nitrogen generator.

3. A nitrogen generator is used to separate nitrogen from the atmosphere under pressure. The compressed nitrogen generated by the nitrogen generator is maintained in a nitrogen storage tank at a set and predetermined pressure, as needed or continuously.

4. The basic function of a pressurized nitrogen storage tank is to maintain a sufficient amount of inert nitrogen to continuously cover the empty space of the associated fuel storage tank at a predetermined pressure. The pressurized nitrogen storage tank also provides a sufficient amount of inert nitrogen to:

A. the interstitial spaces of the associated fuel tanks are continuously filled with inert gas via separate conduits and possibly other exhaust gaps.

B. The air gap or headspace of the associated canister is tested for leaks according to a selected or programmed schedule (c.a.r.b.tp-201, ST-27, ST-30, VMI-10).

C. Sufficient pure nitrogen is provided to perform scheduled or unscheduled third party tests (c.a.r.b.tp-201, ST-27, ST-30, VMI-10) on related or unrelated fuel tanks.

D. Sufficient pure nitrogen is provided to enable the sale of nitrogen, for example, to allow a driver to inspect and inflate a tire with nitrogen (preferably, at least 80 PSI is provided).

5. And (4) selling nitrogen. Excess inert nitrogen is sold to provide additional site retail or equipment compensation revenue sources.

The NBS controller is responsible for detecting fuel movement and adding nitrogen to replace the fuel. The controller is also responsible for conducting a headspace or air gap test if the test is desired or needed at that location. If the nitrogen generator is unable to deliver nitrogen, the controller sends a notification.

In addition to providing a blanket gas protectant in the air gap (and/or gap of the canister), the present invention is also useful for deploying a Volatile Corrosion Inhibitor (VCI), such as via a gas, fog, etc., to the air gap, and/or main gasoline delivery lines, etc., of a retail establishment.

One group of materials for covering fuel (particularly hydrocarbon-based fuel) canisters includes the ZERUST products offered by North technology International Inc., located in Toxon, Minn. VCIs can be infused into stable base materials such as polyethylene (plastic) sheets. When deployed, the VCI is released from the substrate/transport material and a molecular layer of VCI is deposited on the surface of the material to be protected. The VCI works in one of the following ways or in a combination of these mechanisms depending on the application: 1. barrier film (b): wherein the molecular layer prevents corrosive elements from reaching the metal. In some cases, this may also be in the form of a passivation film. PH change: in which the VCI molecules can change the PH of the layer in contact with the metal and prevent corrosion. 3. Clearing: wherein the VCI molecules react with corrosive elements in the environment and convert them into neutral compounds.

VCI products are protected from corrosion in a number of ways. By acting as a protective barrier against external dirt and wear, and also as a barrier to help block the diffusion of corrosive acidic gas contaminants, such as sulfur dioxide or hydrogen sulfide, from the outer packaging material, thereby preventing contact of these corrosive gases with the surrounding metal surface. Vapor corrosion inhibitors that passivate the metal surface by the flow of electrons between the anode and cathode regions and impede the electrochemical corrosion process. By adding hydrophobic properties to the metal surface, water is inhibited from penetrating the metal surface and providing an electrolyte for corrosion reactions. The vapor corrosion inhibitor portion of the product is made of a proprietary chemical formulation that is colorless, odorless, non-toxic, non-reactive, non-flammable, and non-allergenic. These chemical formulations release corrosion inhibiting vapors that diffuse throughout the package and rest on the exposed metal surfaces to form a microscopic corrosion inhibiting layer.

This protective layer will remain on the metal surface as long as there is no significant continuous air exchange within the package. Ideally, there should be less than one air exchange per day (e.g., when the electrical cabinet or package is simply and accidentally opened). Once the metal component is removed from the enclosure, the balance between the corrosion inhibiting layer and the VCI source is broken and no longer maintained, and it dissipates from the metal surface (typically within an hour), leaving a clean, dry, corrosion-free metal component.

The VCI may be a scale-preventing compound. They can be designed to act as a mist protection for the internal empty space of cans, packages and enclosures. This protects ferrous metals and has compatibility with a variety of metals.

The VCI vaporous scale prevention liquid protects ferrous metals by contact with inhibitors. It can also be used as a pressurized spray. VCI molecules migrate to provide protection even in hard to reach areas within an enclosed space. The rust preventatives form a clear, thin, dry-to-the-touch coating and are safe to use on most painted surfaces, rubber seals and plastics. It is compatible with other metals such as aluminum, copper, brass, and nickel alloys.

However, there is still a need to properly incorporate VCIs into the fuel system. The present invention employs a gas blanketing system to spread the VCI over the surface of the fuel system. The VCI may be dispersed into the gas gap of the canister with an inert gas or a cover gas to provide a coating to the system surfaces. By integrating the cover system, VCI can be continuously supplied to the tanks and supply lines. In a preferred embodiment, the VCI will not be subjected to any additional pressure and may be drawn via the Venturi (Venturi) effect during the fuel supply cycle or during the gap treatment. Alternatively, the VCI may be entered at one or more particular times or intervals as desired. The VCI may be stored in a pressurized container and paid out in a separate activity to deliver a specific amount of VCI, in which case sufficient pressure and volume will be provided to cause the vent to open, thereby coating the entire exposed canister and venting system (preventing the formation of rust in the vent).

The system may include a VCI storage/source coupled to the controller to open the VCI source valve while simultaneously opening the gas blanketing valve to provide a carrier of the VCI (e.g., in the form of a mist) into the storage tank. By utilizing the venturi effect, the unpressurized VCI source can be drawn into the supply line and into the canister and mixed with the cover-up to evenly coat the air gap and supply line of the canister.

In alternative embodiments, the VCI may be pressurized and introduced with the cover gas, or introduced separately or sprayed onto the tank wall. The introduction and application of VCIs may include a separate activity to deliver a predetermined level of VCI into the system. The VCI may also be sent as a pressurized spray to coat the canister and cause the pressure relief system in the canister to open, forcing gas out of the air gap and relieving the pressure in the line. By coating the pressure relief line, it is possible to prevent the upper portion of the fuel storage system from rusting and to prevent the rust from bursting and falling back into the fuel.

VCI is also used to coat and protect sulfur dioxide from diesel exhaust in automotive motors, thereby preventing acids (i.e., sulfuric acid) from attacking the vehicle's tanks and motor system piping. The VCI may be used on a re-exhaust fluid and to line the tanks of a truck.

The present invention includes a method of efficiently using a pressure system for more than one purpose; where the demands may have different pressure demands; where different priorities exist for the use of pressure/fluid. A system performing this method can efficiently store and use pressure/fluid to meet more than one requirement simultaneously using a pumping system.

The invention includes prioritizing resources (pressure/fluid) for more than one requirement (taking into account contention priority); thereby reducing the number of pumping systems and components; reducing utility costs by reducing the number of pumping systems through the use of larger, more efficient pumping systems; reducing the number of pumping systems and hence maintenance costs by using a larger, more efficient pumping system; and to reduce monitoring costs by reducing the number of pumping systems.

For the NBS system, there are three key points. First, the system should dry the air and remove water vapor from the air gap (gap, etc.). The preferred system can inject dry air into the air gap because untreated air entering the air gap can cause the problems described above. A preferred embodiment of the present invention includes the provision of injected dry N2. Water can still enter the air gap if it finds an independent vent path (gasket, fitting, manhole or other slack porous device that does not seal to water vapor entering the air gap) into the tank. The water together with O2 and moisture allowed the growth of the acetobacter bacteria. The aggregation of N2 provided reduces or eliminates O2, thereby reducing bacterial growth. N2 or other inert gases are more preferred, although dry air is also useful.

Second, the present invention provides means for filling the air gap with an inert gas that will kill, inhibit or inhibit bacterial growth, thereby preventing acidic liquids from being produced or deposited in the air gap as vapors, or entering the fuel in the UST/AST along with other water vapors and deposited moisture. N2 is preferred because it can be produced inexpensively at the site. Prior art solutions include ships using exhaust gas to clean/cover the air gap. The reason for this is to ensure the safety of these boats, but this has the side effect of reducing the moisture and killing the bacteria. An alternative to the nitrogen embodiment would be to use a pressurized vessel or bottle with the inert gas reducing the O2 content when blown into the air gap.

Detailed Description

The present invention is used by modifying existing systems in the most preferred form or by creating new systems.

Existing system equipment improvements

Referring to fig. 1, a pressure/vacuum (p/v) control valve 1 is installed above the ground and in one or more exhaust pipes of the tank. The overall operating positive and negative ullage space pressures of the test tank are now controlled to be within the p/v control valve parameters.

The checked low pressure regulating control valve 4 is connected to the exposed tank vent pipe 2 below the tank vent p/v control valve 1. An inert gas line is connected to the low pressure regulator control valve being checked, either below (as shown) or along the vent line. The other end of the inert gas line was connected to a compressed nitrogen reserve and fed from there.

The pressure regulating valve 4 is arranged to allow inert nitrogen to flow from the transfer valve 5 to enter the tank when fuel is dispensed. The basic dynamic principle is that the valve senses the low pressure in the headspace connected to the tank storing the fuel and delivers nitrogen accordingly. The positive headspace pressure was set as low as 0.1 inch of water is sufficient, as the tank drains fuel and the liquid level drops, the pressure drops and nitrogen is added. As the canister refills with hydrocarbon fuel, the pressure rises and nitrogen exits through a preset exhaust port p/v valve.

Retail gas stations are not equipped with a blanket gas system because irregular fuel dispensing is taking place throughout the day. A quantity of nitrogen is an inert blanket gas used to replace air vapor drawn into the empty space of the canister, typically when fuel is dispensed or when an event occurs that would cause the pressure within the headspace of the canister to decrease and draw in ambient air with water vapor (i.e., moisture, rain, etc.).

For testing, the delivery pressure of the reserve nitrogen was adjusted to less than 5PSI, a low pressure regulating control valve connected to the vent standpipe attached to the tank. However, 5PSI is not an absolute value and, considering the diameter of the tube and the example, the pressure must be high enough to allow a sufficient amount to pass through the adjustment orifice and the delivery tube 5 to prevent air vapour from entering the tank, thereby compensating for the reduced level of fuel or other physical property that may reduce the pressure in the tank. Another consideration is sizing the nitrogen delivery system to minimize the potential for over-pressurization of the tank 10. The normal liquid output of the test tank is one factor that allows us to determine that the amount of nitrogen source meets the requirements for the blanket tank, and the number of nozzles dispensing fuel is another factor. There are other factors that determine the source demand.

For testing, copper test strip probes, which are checked and/or set according to a predetermined program, are used as visual controls. Once the canister test apparatus is installed, the test canister is allowed to operate normally in an open atmosphere for a period of time, for example, 30 to 90 days. Copper tape visual inspection was used to detect low or high PH in the empty space of the test tank. If the copper test strip shows an acidic condition, this indicates a failure to significantly reduce or eliminate the growth of Acetobacter bacteria. The test strip sample will be visually compared to the previously obtained test strip sample.

The P/v sensing sensor is mounted below the test tank P/v control valve and has a narrow sensing range, for example, between plus 10 inches of water and minus 10 inches of water. The P/v sensing sensor signals communicate with one or more devices, which may include one or more proportional valves, one or more non-proportional valves, event data recorders, computing devices, control devices, algorithms, event parameters, response parameters, alarm and notification potentials, communication devices, and other devices not mentioned. Alternative to existing system modifications 2

The P/v control valve is mounted on the above-ground riser stack of the tank. The overall operating positive and/or negative ullage pressure of the test tank is controlled by a p/v control valve mounted on the tank's vent stack.

The low pressure regulating control valve examined was connected below the vent p/v control valve of the tank and to the above ground vent riser of the tank and to the compressed nitrogen reserve source (from which the inert gas was fed). The pressure regulating valve is set to allow the inert gas to flow into the tank when the fuel is dispensed. The basic dynamic principle is that the valve senses the low pressure in the headspace connected to the tank storing the fuel and delivers nitrogen accordingly. The positive headspace pressure was set as low as 0.1 inch of water is sufficient, as the tank drains fuel and the liquid level drops, the pressure drops and nitrogen is added. As the canister refills with hydrocarbon fuel, the pressure rises and nitrogen exits through a preset exhaust port p/v valve.

The reserve of compressed nitrogen is an inert blanket gas used to replace the normal resident atmosphere in the empty space of the tank being tested. For testing, the delivery pressure of the reserve nitrogen was adjusted to less than 5PSI, a low pressure regulating control valve connected to the vent standpipe attached to the tank. The normal liquid output of the test tank determines that the nitrogen source reserve meets the blanket tank requirements.

A copper test strip probe, checked and/or set according to a predetermined program, is used as a visual control. Once the canister test apparatus is installed, the test canister is allowed to operate normally in an open atmosphere for 30 to 90 days. Visual inspection by copper tape may or may not confirm a low PH in the empty space of the test tank. Assuming that the copper test strip indicates the presence of an acidic condition or anaerobic activity within the empty space of the test canister, the test strip sample will be visually compared to a test strip sample subsequently taken over a period of 30 to 90 days with the empty space of the test canister covered by nitrogen.

The P/v sensing sensor is mounted below the test tank P/v control valve and has a narrow sensing range, for example, between plus 10 inches of water and minus 10 inches of water. The P/v sensing sensor signals communicate with one or more devices, which may include one or more proportional valves, one or more non-proportional valves, event data recorders, computing devices, control devices, algorithms, event parameters, response parameters, alarm and notification potentials, communication devices, and other devices not mentioned.

The present invention may include a novel method for detecting leaks. Separate temperature and/or pressure gauges may be installed in or floating within the tank, or located somewhere along the exhaust system. Pressure readings may be taken from the tank space to determine when blanket gas should be delivered to the system. In a normal daily operating cycle, the temperature will vary (with seasonal variations, etc.) and the system must be configured to distinguish between temperature/pressure variations based on environmental factors and operating factors. There may be multiple gasoline dispenses that occur during the day. When each petrol dispensing time occurs, if the pressure in the canister falls below a preset threshold, N2 will be released into the air gap by action of the controller. The P/v sensing sensor is mounted below the test tank P/v control valve and has a narrow sensing range, for example, between plus 10 inches of water and minus 10 inches of water. The P/v sensing sensor signals communicate with one or more devices, which may include one or more proportional valves, one or more non-proportional valves, event data recorders, computing devices, control devices, algorithms, event parameters, response parameters, alarm and notification potentials, communication devices, and other devices not mentioned. The collected data provides information that can be viewed in a variety of formats, and such data can be analyzed, tested, compared, and used to determine events (including leaks, leak rates, fuel delivery times), other events (including pressure events), and other seemingly unrelated events, such as thieves. The flow of N2 into the canister will be triggered when fuel leaves the canister, when a customer is refueling, or even a minor leak that will allow vapor pressure to leave the canister. Testing the container for air gap leaks, potential vapor loss (PVA), and water intrusion points can solve the problems of slow liner degradation, loose or improper threaded connections or seals, no cap replacement, etc. The threshold is set below the level that it is desired to maintain when re-pressurization is initiated. There are a number of ways to distinguish between a refueling event and a leak. These include the amount and volume of pressure drop. This, along with statistical estimates of other pressure data collected, allows us to detect leaks, quantify them, and distinguish them from refueling events.

When the test tank receives a bulk fuel delivery. It is desirable for the p/v valve to open to relieve excess pressure. If other components (such as the stage 1 vapor control system) are operating properly, N2 or saturated hydrocarbons will flow out of the canister and into the transfer truck.

When the test canister dispenses fuel to the consumer. The flow of N2 into the canister will be triggered when fuel leaves the canister, when a customer is refueling, or even a minor leak that will allow vapor pressure to leave the canister. The threshold is set below the level that it is desired to maintain when re-pressurization is initiated. There are a number of ways to distinguish between a refueling event and a leak. These include the amount and volume of pressure drop. This, along with statistical estimates of other pressure data collected, allows us to detect leaks, quantify them, and distinguish them from refueling events.

Fuel storage tanks have multiple cycles, such as when the tank receives bulk fuel delivery or refilling, or when the test tank dispenses fuel to the consumer. When the P/v valve opens to vent nitrogen to atmosphere or trigger refill absorption of nitrogen is designed to inert or cover the empty space of the test tank. Some are at low pressure, while other tanks may be maintained at different pressures depending on the environmental conditions, the type of use of the tank, etc. For example, when N2 needs to fill the top of the air gap (venting environmental factors), a leak may be detected. In addition, the leakage remains relatively constant over the normal time that the "tightness" needs to be assessed, and the fuel sold varies with the number of refueled consumers. This may also be combined with monitoring the amount of hydrocarbon product dispensed to determine the integrity of the fueling system.

Referring to fig. 1, in the present invention, nitrogen may be separated to act as an inert blanket gas in the air gap 11 above the liquid fuel 12 of the tank 10. The inner wall 13 of the tank must be kept clean and clear to ensure the safety of the tank system. The gap 15 is the portion between the tank wall 13 and the outer wall 14. An air compressor 20 provides a supply to a nitrogen generator 21. The nitrogen generator may be any N2 generator known in the art to separate and collect nitrogen from the mixed gas. In some cases, the stored nitrogen may be replaced with a compressor and nitrogen generator. In some cases, the stored nitrogen may be replaced with a compressor and nitrogen generator.

In one embodiment, N2 has a dual function, namely canister air gap protection and distribution for use, for example, at a tire inflation point. In this case, nitrogen is directed from the generator to distributor reservoir 22. The dispenser reserve may be routed along line 50 to main compression N2 vessel 3 (as shown) or may be separately positioned to receive N2 when the pressure in the dispensing vessel is below a threshold. The vending machine 24 is arranged after the pressure regulator in terms of dispensing. A hose 25 may be provided, such as for inflating a tire. Optionally, a regulator that releases pressure above 90PSI or the like may be placed before the N2 compressed reserve to ensure that the pressure in the reserve is not too high or too low.

In a preferred embodiment of N2, the main N2 reserve is compressed, preferably above 90 PSI. Downstream of the main reserve is a pressure regulator 7, the pressure regulator 7 leading to an intelligent system controller 30. The system controller 30 provides delivery of the N2 gas to the hydrocarbon canister 10. The system controller may also be provided with the capability to monitor and measure the pressure within the canister. The N2 tank feed line and the pressure monitoring line may be the same, or may run on different lines (for the purposes of faster, more accurate, and constant pressure monitoring). A main valve 31 may be provided along the first conduit 32 to test and monitor the pressure in the tank, and a second or additional valve 33 along the second conduit 34 may be used to supply N2 to maintain delivery. Depending on the level of controller precision, conduits 32 and 34 may be separate or combined.

N2 is provided to the canister through an N2 multiport coupling 35 and into the air gap 11. N2 displaces air in the air gap and stays above the liquid (or solid) fuel. While the air space may also include hydrocarbon vapors, N2 does not readily mix with hydrocarbons. N2 is generally lighter than hydrocarbon vapor and therefore remains at the top of air gap 11 and at upper exhaust pipe 2. Displaced gas may exit via a pressure relief device 1 located at the top of the tank outlet. The air gap vent 36 is an optional access point that may be permanently installed as a valve access point in two size ports (e.g., in an N2 multiport coupling, multiport (threaded permanent/semi-permanent), etc.). The availability of a large number of access points in a link/block configuration is further illustrated in fig. 5-8. Such permanently installed access ports allow easy access to manual meters, sensors, data loggers, while samples can be collected at this point to determine a number of things, such as N2, O2, relative humidity, etc.

It is expected that the N2 provided into the air gap will be a low pressure, in order to limit turbulence and safety, since UST and AST are both (relatively) low pressure tanks. It is recommended to keep the nitrogen delivery pressure low to prevent over-pressurization of the tank in the event of multiple or series of safety incidents (e.g., vents, etc.). The circuit does not necessarily have to be low pressure, and in normal operation, even in a low pressure tank, the system responds even faster to the fuel demand and to a high volume with high pressure. High voltage applications also exist where high voltages are desired, even where high voltages need to be used. It may be preferable to include high pressure N2 in the higher pressure tank, for example, to prevent the liquid from transitioning to a gas/vapor state. It is contemplated that in the future there will be upgraded safety equipment canisters, into which high pressure sources of nitrogen may be incorporated. A high pressure source such as N2 is preferred when the gap is periodically cleaned, and in such an embodiment, the controller should be able to be set with a predetermined N2 gas pressure when N2 is provided to the air gap, etc.

While in some future examples, the pressure/vacuum (p/v) valve may include a one-way check valve (only letting air out as pressure relief), current tank systems are not designed for high pressures (e.g., recommended maximum of 5 psi/burst pressure of 7-8 psi). Typical canisters of current retail systems must be capable of venting under vacuum (even in relatively small amounts) to avoid wrinkling or even inward rupture.

The manual gauge 37 may optionally be mounted on a mechanical psi/vacuum gauge as a temporary or permanent fixture in the system. This may be one embodiment of a pressure sensing article to provide information to a controller and/or a manual reading. The adherent pressure correction gauge 38 may optionally be included, such as in a drop tube installed in the UST or AST (underground or above ground storage tank), and the drop tube may have a seal that separates the air gap (empty space in the tank) from atmospheric pressure except through the fuel in the column (drop tube) or through the atmosphere of a vent with a p/v valve function. To the extent that the p/v valve maintains pressure above or below ambient air pressure, there are different fuel levels between the drop tube and the tank. Manual adhesion into the drop tube may be coordinated with the actual fuel in the canister, outside the drop tube, by reading the pressure differential using a gauge.

A separate conduit 250 may be used to clear the gap 15. The driven N2 may move along the conduit 205 from the controller 30 according to the same or different pressures used in the cover system. The gas provided by the gap moves directly to the gap (because there are no excessive turbulence problems) rather than through the coupling 35. The gap may be vented separately (possibly through a one-way valve) at the gap vent 16, which vent 16 may be treated occasionally or continuously.

In one embodiment of the system, a VCI reserve or VCI source 200 may be included. The VCI processing may be managed by a controller. For example, for an airgap process, the VCI may be dispersed concurrently with the N2 blanket gas, or dispersed all at once, or dispersed all the time, or dispersed at predetermined time intervals or N2 blankets. In addition, a separate conduit 202 may be used to supply VCI from a separate VCI source 201 into the air gap (either together with N2 gas, or separately). The covering of the gap can be done by the same source 200, but also by additional sources 201.

When N2 is placed on top of the hydrocarbon fuel, N2 provides pressure against the incoming air and associated water vapor. The hydrocarbons are distributed via a submersible pump below the level of the tank. As the pressure in the canister decreases due to pumping and the level of hydrocarbon fuel drops, the system controller activates the release of N2 gas into the air gap, rather than allowing the low pressure to continue to remain, or to vent, to atmosphere and possibly water vapor.

Referring to fig. 5-8, the N2 multi-port coupling/nitrogen connection coupling is shown in detail. Coupling 400 may include a plurality of openings having different sizes suitable for various uses. In this case, a hole 401 is drilled on each side 402. The bore 401 is preferably threaded to allow engagement with a complementary threaded conduit (or other article). It is contemplated that the coupling of the present invention replaces the typical coupling used in the prior art because standard couplings are typically too thin to be drilled and threaded to the industry standard to modify the number or depth of threads. The coupling may include six sides 402. The preferred coupling 400 provides a particular mounting height 404 in the exhaust. Height 404 may include a height 404b from bottom 410 to the hole and a spacing 404a from the hole to top 411. The coupling further includes a cavity or chamber 403 in the bottom 410, the cavity or chamber 403 assisting in the present invention and may be used to reduce turbulence of incoming nitrogen gas to prevent vapor excited in the air gap. The chamber wall may be threaded to engage the canister system. As shown in fig. 8, the coupling may include a rounded edge 405 having a width 406, which is flat in fig. 7. The link has a width 407.

One advantage of the system includes the ability of the system controller to test the pressure in the tank. As hydrocarbons are dispensed (e.g., at the fuel pump), the pressure in the canister drops and N2 enters and begins to be replaced. Referring to fig. 2-3, after each dispensing event, the system controller will stabilize the canister and repressurize the canister with N2 gas. When N2 entering the canister exceeds the amount needed to replace the fuel, leaks or other system problems may arise. For example, if the valve delivering N2 is continuously open, this may mean a leak. The amount of fuel dispensed may also be monitored to determine the amount of replacement N2 (taking into account known temperatures and pressures). The N2 dispensing can be monitored by weight.

As shown in fig. 2 and 3, the distribution events throughout the day demonstrate a working system. Dispensing in retail fueling stations or stations typically involves opening a nozzle to dispense fuel (e.g., into a truck), and each station may have a single fuel tank associated with multiple nozzles (typically 1-6 nozzles). Fig. 2 shows the fuel distribution and the effect on pressure over the whole day. Fig. 3 shows a close-up of a refuelling example (fuel dispensing takes approximately 1.5 to 4 minutes) and re-pressurisation (which may start at the initial dispensing of fuel and finish after approximately 1 second after the end of fuel dispensing). As the pressure in the tank is measured by an accurate monitoring system, the amount of N2 and the integrity of the system can be monitored. The system controller can measure and detect a slight pressure differential by maintaining the tank pressure within about 2 "water column pressure (1psi 26.5" water column, 1 atmosphere approximately 15psi) in the tank. Preferably, the pressure is maintained between 1.9 "and 2" water column pressure readings.

As shown in fig. 2, a 24 hour cycle is shown. The pressure 500 in the tank system is shown in inches in a water column. Refueling from the tank system triggers inert gas blanket dispersal through a vent opening event 501 (not fully labeled). The inert gas height during valve opening is represented vertically from 100 to 260. The inert gas system valve is shown closed at 100 and fully open at 260. A typical event includes simultaneous refueling of one to four nozzles. These two-nozzle dispensing events 502 and four-nozzle dispensing events 504 involve valve openings. A large number of events showed that the pressure in the system dropped below 1.9 "at least four times a day. These dips 505 indicate a partial failure of the overlay system to fully compensate for refueling or other pressure drop events. In particular, event 506 represents a significant drop in the pressure of the system to 1.6 ", resulting in the inert gas valve 507 being simultaneously opened to a maximum of 260. This means that the inert gas is sufficient to overcome this event, or the p/v vent is opened to allow the ambient air to re-stabilize the pressure in the system. The irregular event 510 represents an abnormal rise in pressure around 3: 30. To date, this appears to be a change in thermal/temperature events that result in a pressure increase.

As shown in fig. 3, approximately tens of fueling events occur during a day. This represents a busy system. Specifically, a stabilization event 610, etc., near 4:00 shows that the pressure in the system stabilizes between 1.9 "and 2". The refueling event 601 represents a single or multiple refueling nozzles in the system opening, resulting in the inert gas being re-pressurized/compensated. Event 602, etc. shows a first refueling nozzle in use, followed by a turn to a second refueling nozzle, where the first event ends and the second event ends, a 1-2-1 nozzle opening event.

While pressure changes at the 1, 10 "or 1/300" psi level are currently occurring, it is anticipated that greater precision may be desired for other thresholds and sensitivities. The current apparatus can provide greater precision. In addition, the algorithms currently used and the current statistical analysis methods allow for greater sensitivity. It is envisioned that the system controller may measure and monitor water pressures up to 1/1000 ".

The NBS system improves the quality of the fuel, which is particularly useful in standby generators that are not frequently filled/refilled. N2 replaces O2 and H2O in the air gap air to prevent reaction with diesel and other fuels previously mentioned. N2 reduces evaporation of fuel, degradation of fuel and prevents damage to the canister and canister equipment.

An additional feature of the present invention is the reduction of oil vapor intrusion (PVI). PVI occurs when hydrocarbons from the storage tank leak into the ground through various holes, openings, or corrosion in the system. Since N2 is the lightest material, N2 is above and exits first when the air gap is exposed (including through the aperture of the can itself).

The present invention includes a pressurized source of inert vapor/gas generation or supply. For example, a bottled source of inert gas, a p/v valve in combination with a vent, and a pressure regulator set that releases only 2-4 inches of water of inert gas. The P/v valve can hold 6 inches of water. When fuel tanks are used (e.g., heating oil, and generators burning small amounts of fuel each month, and generators for short-term emergencies), inert gas may be injected into the tank system. Rail vehicles and other mobile tanks/containers that transfer, carry, contain and load/unload explosive fuels or gases can also be filled with inert gas by the present invention. The potential for rail vehicle explosions when vented is reduced by automatic replacement of inert gas, and the high pressure supply of nitrogen or other inert gas can help maintain pressure within these systems to reduce evaporation of liquid fuel.

The present invention also includes a method of testing a system to avoid pressure decay and further testing to determine leaks. Typically, the tank is opened for testing and the system is not necessarily completely shut down. The continuous use and repeated pressurization of the canister ensures that the canister pressure (and leakage) is continuously checked to determine if it is tightly sealed. An important item is to distinguish between temperature (i.e., high/low per day, high/low per hour, high/low per season, etc.) and changes in atmospheric pressure. In view of the accuracy of the pressure monitoring system, such items must be considered to determine whether a decrease in system pressure is simply caused by a drop in temperature within the tank/air gap.

The following is a description of a method that may be used with a pressure delivery system as shown in FIG. 4. The primary function of the system is to vent N2 and the secondary function is to fill the tank. The use of this method is for the following cases: the primary function of the delivery system is to maintain a minimum pressure/volume of fluid (vapor or liquid) for a particular function, such as filling a tire. While it appears obvious once described, the art has not used this approach to control or configure.

In this case, we use 100psi as the minimum pressure required for the primary function. There is also a maximum pressure for the base tank 100, which is set to 135psi for purposes of illustration. There is also a secondary use or need for fluids. As long as the primary pressure vessel 100 maintains a minimum pressure (100psi), fluid may be used or diverted from a primary function to flow into a hose, line or tank to use, control, direct or store the excess fluid available from the delivery source under pressure. In this embodiment, the secondary function 104 has one or more uses that can utilize excess fluid/pressure, but does not require the same pressure as the primary function. The secondary use may use the additional pressure as it is delivered or it may be stored in one or more secondary containers.

For example, a major system may require the presence of a 5 gallon pressure vessel 101 that maintains at least 100psi to inflate the tire. If the tank falls to 100PSI (monitored by a pressure sensor), the compressor (part of the main tank 100, along with the compressor, nitrogen generator) moves air through the nitrogen generator 100, and the nitrogen generator 100 should be activated to maintain the main tank 101 at or above 100 PSI. The primary container 101 has a valve that acts as a pressure relief or solenoid valve to allow flow from the nitrogen generator into the tank 101 along conduit 105 and out to the tire inflation apparatus 106 but does not allow fluid (nitrogen) to reach the secondary system 103 or destination 104 unless the primary source tank 101 is determined to be at or above the desired pressure (100 psi).

The secondary system may use nitrogen (or air or liquid) in excess of the primary system requirements. The secondary system may be used to deliver excess full load pressure or may be used to deliver a demand or purpose that is less than the full load pressure of the primary system. For example, nitrogen used to inflate tires may also be used to cover the top of the fuel or to prevent air from being drawn into the air gap or headspace of the UST or AST, as desired. The delivery system responds to the pressure in the primary tank and the demand of the secondary system. Fluid is allowed to flow into the secondary tank as long as the pressure is 100psi above the minimum pressure of the primary tank. When the pressure of both the primary and secondary tanks reached 100psi, the pressure flowed equally into the primary and secondary tanks. In this example, when the pressure in the main tank reaches 135psi, the flow is prevented.

Control of the compressor or pump that provides pressure to the desired system is important for efficiency and economy. It is important to ensure that the allowable events for the device do not exceed the manufacturer's recommended standards. A system that responds only to pressure as described above may require the delivery system to operate continuously. For equipment that is not rated for sustained use, this may lead to system failure due to premature equipment failure. A control system that monitors the run time of the pump/compressor may protect such equipment. The control should be such that the run time is set not to exceed the device parameters or can be changed to be set such that the run time is satisfactory for devices that have been replaced during the lifetime of the system. By limiting the secondary use to the particular equipment providing pressure so as not to compromise the required downtime or downtime, it is ensured that the needs of the primary system are met and that there is sufficient downtime or rest time to prevent compressor damage.

For this type of control device, special considerations are required to ensure that plant operating parameters are followed. Compressors equipped with pressure responsive control respond only to pressure demands. This arrangement may result in continuous operation of the device. Some compressors are not set to run continuously, such as reciprocating, screw, scroll type compressors are manufactured to ensure that the pressure/volume required to fill the primary function is then determined, and then the specification of the compressor CFM with the required pressure is determined along with the appropriate reservoir size to ensure that the volume required for the primary purpose does not cause the compressor to run longer than the manufacturer specified.

Other efficiencies, such as lift, equipment, and daily temperature need to be included in the CFM/pressure calculation. In addition, the volume required for the secondary use should be considered, it being important to meet the required secondary volume of 1-100%. The available run time to meet this need should be considered, followed by the sized volume and pressure and the required (pressure compensated) storage volume.

The type of compressor (such as reciprocating, screw, scroll) and the speed/volume of the compressed air produced is determined by the compressor. For best practice, if the reciprocating compressor should have only 50% duty cycle and a maximum run time of 15 minutes, the compressor should only be turned on when air is needed, or when the pressure in one of the reserves is below a set low threshold, and run no more than the maximum run time. For example, the next compressor "start-up" is triggered when the nitrogen reserve goes below 100 psi. In another embodiment with two nitrogen reserves, or in an embodiment with a compressed air reserve (used as compressed air) and at least one nitrogen reserve, the threshold value can be set by all reserve tanks to trigger the compressor.

One aspect of the invention includes a method of introducing nitrogen from a high point or apex in a controlled, non-turbulent manner in a system. This allows the nitrogen to blanket the hydrocarbons and reduces the mixing of the nitrogen and hydrocarbons.

The embodiments set forth in the description of the present application are for illustrative purposes only and should not be taken as limiting the invention as described and presently claimed. The terms nitrogen and N2 generally refer to molecular nitrogen and nitrogen, respectively. However, in this specification, the two are interchangeable, or reference is made to nitrogen in the conventional sense.

Claims (14)

1. An apparatus for preventing degradation of a double-walled fuel storage tank, the apparatus comprising:

(a) a nitrogen generator supplying a source of pressurized nitrogen gas;

(b) a compressed nitrogen gas source connected to the nitrogen generator to supply pressurized nitrogen gas;

(c) a controller connected to the source of compressed nitrogen for controlling the release of the pressurized nitrogen;

(d) a first conduit interconnecting the controller with the air gap of the double-walled fuel storage tank;

(e) a valve connected to the first conduit and configured to control the flow of the pressurized nitrogen gas through the first conduit into the air gap;

(f) a pressure vacuum valve that controls the separation of negative or positive pressure in the double-walled fuel storage tank from ambient atmospheric pressure;

(g) a vent for venting said nitrogen gas from said air gap when said double-walled fuel storage tank is replenished with fuel; and

(h) a secondary conduit connected to the controller and in fluid communication with a gap between an inner wall and an outer wall of the double-walled fuel storage tank to allow the pressurized nitrogen gas to flow into and/or through the gap.

2. The apparatus of claim 1, further comprising a monitor for testing a pressure within the double-walled fuel storage tank and a relay system for sending information related to the pressure within the double-walled fuel storage tank to the controller.

3. The apparatus of claim 1, further comprising a programmable system programmed to respond to a pressure drop within the double-walled fuel storage tank and supply a determined amount of nitrogen gas into the double-walled fuel storage tank to maintain a stable pressure within the double-walled fuel storage tank.

4. The apparatus of claim 3, wherein the amount of nitrogen determined to be supplied by the controller is determined by weight.

5. The apparatus of claim 2, wherein the monitor is further adapted to control the filling of nitrogen into the air gap to achieve a predetermined pressure within the double-walled fuel storage tank.

6. The apparatus of claim 1, further comprising a nitrogen gas distribution hose for selectable directional distribution of nitrogen gas from the nitrogen generator.

7. The apparatus of claim 6, further comprising a secondary nitrogen reservoir to receive nitrogen from the nitrogen generator and supply the nitrogen to the nitrogen distribution hose.

8. The apparatus of claim 1, further comprising a source of volatile corrosion inhibitor connected to the first conduit, wherein the volatile corrosion inhibitor can be pumped to enter the air gap with the nitrogen gas.

9. The apparatus of claim 1, further comprising a multiport coupling connected to the first conduit and configured to reduce turbulence of incoming nitrogen gas entering the double-walled fuel storage tank.

10. A method of controlling hydrocarbon release from a double-walled fuel storage tank, the method comprising the steps of:

filling the double-walled fuel storage tank with fuel;

filling a top portion of an air gap of the double-walled fuel storage tank with nitrogen from a nitrogen source;

monitoring pressure within the double-walled fuel storage tank;

filling a top portion of the double-walled fuel storage tank with additional nitrogen when a pressure within the double-walled fuel storage tank falls below a predetermined threshold; and

providing a dry inert gas to an interstitial space between an inner wall and an outer wall of the double-walled fuel storage tank.

11. The method of claim 10, further comprising the step of covering an inner surface of the double-walled fuel storage tank with a volatile corrosion inhibitor.

12. The method of claim 10, further comprising the step of dispensing nitrogen from the nitrogen reservoir to the nitrogen dispensing hose.

13. The method of claim 10, wherein the step of monitoring the pressure within the double-walled fuel storage tank detects the timing and proportion of a top-fill event, and further comprising the step of detecting a leak at a pressure in the range of 0.1 inches of water.

14. An apparatus for preventing degradation of a double-walled fuel storage tank, the apparatus comprising:

(a) a source of pressurized compressed inert gas;

(b) a controller connected to the compressed inert gas source for controlling the release of compressed inert gas;

(c) a first conduit interconnecting the controller with the air gap of the double-walled fuel storage tank;

(d) a valve connected to the first conduit and configured to control the flow of the compressed inert gas through the first conduit into the air gap;

(e) a pressure vacuum valve that controls the separation of negative or positive pressure in the double-walled fuel storage tank from ambient atmospheric pressure;

(f) a gas vent for venting gas within the double-walled fuel storage tank; and

(g) a secondary conduit connected to the controller and in fluid communication with a gap between an inner wall and an outer wall of the double-walled fuel storage tank to allow the compressed inert gas to flow into and/or through the gap.